TGFβR Inhibition Represses TGF-β1 Initiated Keratin-7 Expression in Human Salivary Gland Progenitor Cells

Towards the goal of engineering an implantable salivary gland for the treatment of xerostomia, we culture primary human salivary gland stem/progenitor cells (hS/PCs) in hyaluronic acid (HA)-based hydrogels containing a covalently conjugate integrin-binding peptide (RGDSP). We characterize how RGDSP affects hS/PC phenotype and discover the presence of cells expressing both amylase and keratin-7 (K7) in our 3D cultures. Typically, amylase is expressed by acinar cells, and K7 is found in ducts. After assaying an array of transforming growth factor-β (TGF-β) superfamily members, we find increased expression of TGF-β1 and growth/differentiation factor-15 (GDF-15) in RGDSP cultures. However, 2D model studies confirm that only TGF-β1 is required to induce K7 expression in hS/PCs. We then demonstrate that with pharmacological inhibition of TGF-β signaling, K7 expression is repressed while amylase expression is maintained in RGDSP cultures. Thus, TGF-β signaling regulates K7 expression in hS/PCs, and modulation of TGF-β signaling is essential for the regeneration of salivary gland function.

Non-Lethal Concentration of MeHg Causes Marked Responses in the DNA Repair, Integrity, and Replication Pathways in the Exposed Human Salivary Gland Cell Line

In Brazilian northern Amazon, communities are potentially exposed and vulnerable to methylmercury (MeHg) toxicity through the vast ingestion of fish. In vivo and in vitro studies demonstrated that the salivary glands as a susceptible organ to this potent environmental pollutant, reporting alterations on physiological, biochemical, and proteomic parameters. However, the alterations caused by MeHg on the gene expression of the exposed human salivary gland cells are still unknown. Therefore, the goal was to perform the transcriptome profile of the human salivary gland cell line after exposure to MeHg, using the microarray technique and posterior bioinformatics analysis. The cell exposure was performed using 2.5 µM MeHg. A previously published study demonstrated that this concentration belongs to a range of concentrations that caused biochemical and metabolic alterations in this linage. As a result, the MeHg exposure did not cause lethality in the human salivary gland cells line but was able to alter the expression of 155 genes. Downregulated genes (15) are entirety relating to the cell metabolism impairment, and according to KEGG analysis, they belong to the glycosphingolipid (GSL) biosynthesis pathway. On the other hand, most of the 140 upregulated genes were related to cell-cycle progression, DNA repair, and replication pathway, or cellular defenses through the GSH basal metabolism. These genomic changes revealed the effort to the cell to maintain physiological and genomic stability to avoid cell death, being in accordance with the nonlethality in the toxicity test. Last, the results support in-depth studies on nonlethal MeHg concentrations for biomarkers identification that interpret transcriptomics data in toxicological tests serving as an early alert of physiological changes in vitro biological models.

B7-H2 Expression in Human Salivary Gland Epithelial Cells Affects Saliva Secretion in Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a chronic inflammatory autoimmune disease of exocrine gland. In pSS, permanent activation of the adaptive immune system is obvious. Lymphocyte co-stimulation plays an important part in inflammation and immunotherapy. Co-stimulator ligands (B7-H2) are significant costimulatory molecules. The interaction of B7-H2, with its sole receptor ICOS, promotes T cell differentiation, effector responses and activation. Our study found that B7-H2 is up-regulated in salivary gland, saliva and serum of pSS patients. B7-H2 expression in saliva have negatively correlated with saliva weight. Overexpression of B7-H2 into human salivary gland epithelial (HSGE) cells, increased the activity of p65 (phosphorylated at S536) and decreased the expression of AQP5. Furthermore, up-regulated B7-H2 induced apoptosis and inhibited proliferation in HSGE cell lines. These results suggest the expression of B7-H2 can decrease the secretion of saliva, increase the quantity of dental caries and reduce lifespan of patients of pSS.

First person – Shohei Yoshimoto

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms, helping early-career researchers promote themselves alongside their papers. Shohei Yoshimoto is first author on ‘Inhibition of Alk signaling promotes the induction of human salivary-gland-derived organoids’, published in DMM. Shohei is a research scientist in the lab of Professor Shuichi Hashimoto at Fukuoka Dental College, Fukuoka, Japan, investigating salivary gland disorders.

Inhibition of Alk signaling promotes the induction of human salivary-gland-derived organoids

ABSTRACTHyposalivation and xerostomia are the cause of several morbidities, such as dental caries, painful mucositis, oral fungal infections, sialadenitis and dysphagia. For these reasons, preservation of normal saliva secretion is critical for the maintenance of functionally normal oral homeostasis and for keeping good health. Several strategies for restoring salivary gland function have been reported, from different points of view, based on the use of salivary-gland-derived epithelial stem/progenitor cells and tissue engineering approaches to induce organoids that mimic in vivo salivary glands. In this study, we clarified that inhibition of activin receptor-like kinase (Alk) signaling was essential for the induction of human salivary-gland-derived organoids, and demonstrated the usefulness of such organoids as an inflammatory disease model. In inflammatory conditions like sialadenitis, in general, pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α, also known as TNF) are upregulated, but their function is still unclear. In our established human salivary-gland-derived organoid culture system, we successfully induced organoid swelling by stimulation with carbachol, a non-selective cholinergic agonist, and forskolin, an activator of cystic fibrosis transmembrane conductance regulator (CFTR). Furthermore, we found that this organoid swelling was inhibited by TNF-α. From these results, we could clarify the inhibitory function of TNF-α on saliva secretion in vitro. Thus, our established human salivary-gland-derived organoids would be useful for in vitro analyses of the morphological and functional changes involved in salivary gland dysfunctions in several research fields, such as pathobiology, inflammation and regenerative medicine.This article has an associated First Person interview with the first author of the paper.